This invention relates generally to the production testing of phonograph records, and more particularly concerns simple apparatus to test for record groove eccentricity.
When phonograph records are pressed or molded, the resultant spiral grooving may be slightly eccentrically located relative to the record center pin hole. As a result, when the record is played, the tone arm will pivot slightly back and forth radially (relative to the hole) in addition to moving spirally inwardly, and an audibly detectable WOW can and does result if such back and forth movement exceeds a very slight amount. There is a need for easily usable, simple, rugged apparatus to test for such eccentricity so that production workers using such equipment can quickly and easily determine whether a production record should or should not be rejected. There is no equipment to my knowledge which incorporates the unusual advantages in structure, mode of operation and results as now afforded by the present invention.